1. Field of the Invention
This invention relates to a composite working device using a robot, and more particularly to a composite working device in which a robot for use in assembly of vehicle bodies, for instance, is arranged to accomplish transfer of a workpiece in addition to a regular operation such as welding of the workpiece.
2. Description of the Prior Art
Recently, various robots are used, for instance in assembly of vehicle bodies in order to automate production, thereby contributing to labor saving. However, conventional robots are designed to accomplish one operation exclusively. For example, a welding robot exclusively accomplishes welding and a transfer robot exclusively accomplishes transfer of workpieces. Therefore, many robots and a large space have been required for each manufacturing step, thereby adding to the plant investment.
This applicant previously proposed arranging a robot to accomplish both welding and transfer of workpieces. (See Japanese Unexamined Patent Publication No. 58(1983)-151972). In the proposal, the robot is provided with a welding gun and the welding gun is used for gripping a workpiece when transferring the workpiece. However, this arrangement has been found to be disadvantageous in that, because the robot is arranged to grip the workpiece with the electrode of the welding gun which is thin and small, it is not suitable for transferring a large workpiece and the electrode is apt to be damaged.